I think that we discussed this one previously.
Article 225 _Outside_ Branch Circuits and Feeders clearly permits 'shared neutral' circuits for lighting ( 225.7(B) )
Common neutral circuits are also described for _feeders_.
Article 210 does not mention 'shared neutral' circuits. 210.4 defines and permits multiwire circuits, and as described a multiwire circuit is a specific type of shared neutral circuit. But as far as I can tell nothing in article 210 either prohibits or permits shared neutral circuits.
-Jon
